Segment Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 2,886,902	$ 2,660,844	$ 2,819,106
Intangible Assets, Net (Including Goodwill)	5,959,269	4,626,001	4,652,844
UNITED STATES
Segment Reporting Information [Line Items]
Revenues	2,175,721	1,868,076	1,977,975
Intangible Assets, Net (Including Goodwill)	4,240,579	3,134,267	3,135,226
UNITED KINGDOM
Segment Reporting Information [Line Items]
Revenues	242,238	338,552	398,729
Intangible Assets, Net (Including Goodwill)	996,136	820,730	1,062,332
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	468,943	454,216	442,402
Intangible Assets, Net (Including Goodwill)	$ 722,554	$ 671,004	$ 455,286